Plastics used for automotive interiors are weakly resistant to deformation by chemicals, corrosion, UV light or heat in terms of the properties thereof, and have surface defects such as scratches, poor surface quality, limited colors, etc., caused upon injection molding, in terms of the outer appearance thereof. Therefore, in order to alleviate such defects of plastics, a process of applying a solvent-based acrylic lacquer onto the surface of plastics has been conventionally employed.
However, the solvent-based acrylic lacquer is a two-component solvent-based coating comprising an acryl or polyester coating having 10˜30 wt % of a solid content and an isocyanate curing agent. The large amounts of organic solvents contained in the solvent-based coating generate volatile organic compounds (VOCs), thus causing environmental contamination and offensive odors and aggravating the health of workers. Hence, the use of organic solvents is restricted by various environmental laws in foreign countries. Thorough attempts to decrease the amount of solvent used when making a coating have been continuously made according to environmental protection programs led by developed countries.
In addition, the solvent-based acrylic lacquer, that is, an oil coating, suffers because a coating film formed thereof has a cool and hard feeling when contacted by a user, thus resulting in a much poorer texture compared to the texture of natural leather.
With the intention of solving the problems, an aqueous coating has been used instead of the oil coating in the field of plastic parts for automotive interiors. The application of the aqueous coating has received great attention in terms of decreasing the amount of VOCs. Further, the aqueous coating is advantageous from points of view of health and the environment, and as well, may overcome cracks or corrosion of the surface of plastics due to the attack of constituents of the solvent-based coating, for example, a strong solvent such as xylene or methylisobutylketone.
Therefore, the aqueous coating is used in the field of plastic parts for automotive interiors, thereby solving the conventional problems. However, the aqueous coating is disadvantageous because offensive odors are still caused by the presence of the non-reactive monomer of the aqueous acrylic resin used for the aqueous coating and the solvent for use in the formation of the coating film. Therefore, the removal of such odors is required.